5

Ordering information

5.1

Nanopower applications

The TSU111H can operate from 1.5 V to 5.5 V. The parameters are fully specified at 1.8 V, 3.3 V, and 5 V supply

voltages and are very stable in the full VCC range. Additionally, the main specifications are guaranteed on the

temperature range from -40 to 150 °C.

5.1.1

Schematic optimization aiming for nanopower

To benefit from the full performance of the TSU111IY, the impedances must be maximized so that current

consumption is not lost where it is not required.

For example, an aluminum electrolytic capacitance can have significantly high leakage. This leakage may be

greater than the current consumption of the op amp. For this reason, ceramic type capacitors are preferred.

For the same reason, big resistor values should be used in the feedback loop. However, there are two main

limitations to be considered when choosing a resistor.

1.

Noise generated: a 100 kΩ resistor generates 40 nV/√Hz, a bigger resistor value generates even more

noise.

2.

Leakage on the PCB: leakage can be generated by moisture. This can be improved by using a specific

coating process on the PCB.

5.1.2

PCB layout considerations

For correct operation, it is advised to add 10 nF decoupling capacitors as close as possible to the power supply

pins.

Minimizing the leakage from sensitive high impedance nodes on the inputs of the TSU111H can be performed

with a guarding technique. The technique consists of surrounding high impedance tracks by a low impedance

track (the ring). The ring is at the same electrical potential as the high impedance node.

Therefore, even if some parasitic impedance exists between the tracks, no leakage current can flow through them

as they are at the same potential (see Figure 56. Guarding on the PCB).

Figure 56. Guarding on the PCB

5.2

Rail-to-rail input

The TSU111H is built with two complementary PMOS and NMOS input differential pairs. Thus, the device has a

rail-to-rail input, and the input common mode range is extended from (VCC-) - 0.1 V to (VCC+) + 0.1 V.

The TSU111H has been designed to prevent phase reversal behavior.

TSU111H

Ordering information

DS14162 - Rev 1

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